1. Field of the Invention
The invention relates to optical camera systems for nondestructive internal inspection of power generation machinery, including by way of non-limiting example industrial gas and steam turbine engines as well as generators. More particularly aspects of the invention relate to a visible light or infra-red optical camera inspection system that is capable of positioning camera fields of view (FOV) through a gas turbine inspection port, inlet or outlet in any portion of the engine, including the compressor section, combustor nozzle and transition and turbine section, capturing visual images of the engine's internal structure. One or more cameras are mounted within a camera head that is translated to areas of interest within the turbine or other power generation machinery by a flexible tether, so that their respective fields of view capture desired images. The includes a camera head position system that inferentially determines three dimension (3D) position of the camera head, so that the captured images and their position are correlated for future analysis. In this manner images from any inspected position within the machinery can be selectively recalled for review or multiple images can be stitched to create a composite image of the machinery inspected areas.
2. Description of the Prior Art
Power generation machinery, such as steam or gas industrial turbines, are often operated continuously with scheduled inspection and maintenance periods, at which time the turbine is taken offline and shut down. By way of example, a gas turbine engine often will be operated to generate power continuously for approximately 4000 hours, thereupon it is taken off line for routine maintenance, inspection, and repair of any components identified during inspection. Taking a gas turbine off line and eventually shutting it down completely for scheduled maintenance is a multi-day project. Some turbine components, such as the turbine rotor section, are operated at temperatures exceeding 1000° C. (1832° F.). The turbine requires 48-72 hours of cooling time to achieve ambient temperature before complete shutdown in order to reduce likelihood of component warping or other deformation. During the shutdown phase the turbine rotor rotational speed is spooled down from operating speed of approximately 3600 RPM to a speed of approximately 120 RPM or less in “turning gear mode” where the rotor is externally driven by an auxiliary drive motor, in order to reduce likelihood of rotor warping. Other turbine components, such as the turbine housing, are also cooled slowly to ambient temperature.
Once the turbine is cooled to ambient temperature over the course of up to approximately 72 hours internal components of the now static turbine can be inspected with optical camera inspection systems. Known optical camera inspection systems employ rigid or flexible optical bore scopes that are inserted into inspection ports located about the turbine periphery. The bore scope is manually positioned so that its field of view encompasses an area of interest within the turbine, such as one or more vanes or blades, combustor baskets, etc. A camera optically coupled to the bore scope captures images of objects of interest within the field of view for remote visualization and archiving (if desired) by an inspector.
If a series of different images of different areas of interest within a given turbine inspection port are desired, the inspector must manually re-position the camera inspection system bore scope to achieve the desired relative alignment of internal area of interest and the field of view. Relative alignment can be achieved by physically moving the bore scope so that its viewing port is positioned proximal a static area of interest. Examples of such relative movement of bore scope and static turbine component are by inserting a bore scope in different orientations within a static combustor or radially in and out of space between a vane and blade row within the compressor or turbine sections. For rotating blade inspection, relative alignment can also be achieved by maintaining the bore scope viewing port in a static position and rotating the blade row blades successively into the camera static viewing field.
Previously referenced, commonly owned United States publication number 2013/0335530, entitled “System And Method For Visual Inspection And 3D White Light Scanning Of Off-Line Industrial Gas Turbines And Other Power Generation Machinery” and United States patent application publication number 2013/0192353, entitled “System And Method For Automated Optical Inspection Of Industrial Gas Turbines And Other Power Generation Machinery With Multi-Axis Inspection Scope” describes motorized inspection system embodiments that can be automatically maneuvered within power generation machinery or manually maneuvered under control of a human operator. Relative orientation coordinates of the driven motion axes are monitored by the system, so that the inspection camera head position and orientation are known by referencing those axes coordinates.
In other types of power generation machinery internal optical inspection procedures it is desirable to position manually under human operator control a camera head mounted on a flexible tether and record the camera images, as is described in previously referenced, commonly owned United States publication number 2014/0055596, entitled “Flexible Linkage Camera System And Method For Visual Inspection Of Off Line Industrial Gas Turbines And Other Power Generation Machinery”. For example, non-rotating static vane inspections within compressor or turbine section rows require physical movement of the inspection scope camera system field of view to each individual vane. The narrow confines of passages surrounding stationary vanes often will not facilitate passage of traditional inspection scope systems. In order to complete inspection of the vanes, supporting structures, such as vane shrouds are removed to provide sufficient visual exposure and/or passage of inspection scope components within the restricted confines of vane rows.
Thus, complete turbine inspection with a flexible, tethered camera inspection system, such as that described in United States publication number 2014/0055596, requires multiple manual relative repositioning sequences between the camera inspection system viewing ports and other internal inspection access points to allow complete visual inspection of all areas of interest within the turbine. Inspection apparatus positioning is challenging due to the complex, often tortuous manipulation paths between components in a gas turbine. The inspection scope camera delivery system must be sufficiently flexible to insert through tight confined passages, yet not too flexible or limp to prevent controlled positioning within the passages. Unlike the aforementioned motorized multi-axis inspection system that is described in United States patent application publication number 2013/0192353, the flexible tethered camera inspection system does not provide camera head position/orientation information that can be advantageously combined with the optical image information for future analysis or composite image generation.